Resistor type of isolator for lightining arresters



y 1951 H. o. STOELTING ET AL 2,551,858 RESISTOR TYPE OF ISOLATOR FORLIGHTNING ARRESTERS Filed Au '22, 1949 2 Sheets-Sheet l y 1951 H. o.STOELTING ETAL 2,551,858

RESISTOR TYPE OF ISOLATOR FOR LIGHTNING ARRESTERS Filed Aug. 22, 1949 2Sheets-Sheet 2 INVENTORS %7fl10/7 0 ace/2 12 fife v17 5% Qi ve/ePatented May 8, 1951 RESISTOR TYPE OF ISOLATOR FOR LIGHTNING ARRESTERSHerman 0. Stoelting, Milwaukee, Wis., and Joseph F. Kuzela, Oneida, N.Y., assignors to McGraw Electric Company, a corporation of DelawareApplication August 22, 1949, Serial No. 111,726

Claims. 1

This invention relates to resistor types of isolators for lig tningarresters.

rleretofore it has the practice to provide an isolator for lightningarresters which is associated with a lightning arrest-er having sparkgaps and negative valve material and which is so arranged that forordinary discharges, the isolator will not function but for unusuallyheavy discharges which result from breaking down of the valve material,for instance, the isolator will function and permanently open thecircuit to the ground of the lightning arrester. This type of structureis shown in the patent to R. H. E? 'le, No. 2,315,320 of March 30, 1943for Automatic Circuitinterrupting Device, owned by the assignee of thepresent invention.

In. pior forms of isolators attached to the lower end of a lightningarrester and interposed between such lower ends and the ground, it hasbeen found that radiointerference is produced. On investigation, it wasdiscovered that t -i radio interference resulted from the building up ofa potential difference between the upper and lower electrodes of theisolator which resulted in a slow leak to ground across the gap in theisolator, thus producing corona efect with subsequent radiointerference.

Objects of this invention are to provide novel forms of isolator-s whichare of the resistor type and are equipped with a high value resistorbric ng gaps of the isolator and furnishing a discharge path from theupper to the lower electrodes, thereby discharging any charge that mayaccumulate on the upper electrode and preventing the formation of coronawith subsequent radio disturbance.

Furt ier objects are to provide novel forms of isolator-s having thecharacteristics hereinabove enumerated which are of very simpleconstruction and which can be attached to the lower end of lightningarrest and to the ground wire with the utmost ease and which arerelatively inexpensive to replace.

Embodiments of the invention are shown in the accoii panying drawings,in which- Figure 1 is an elevation of a lightning arrest-er with theisolator attached with parts broken away and parts in section.

Figure 2 is an enlarge isolator shown in Figure 1.

Figure 3 is a sectional view of a further form of isolator.

Figure 4 is an enlarged perspective view of a part of the structureshown in Figure 3.

sectional view of the Figures 5 and 6 are sectional views of stillfurther forms of isolators.

Referring to the drawings, it will be seen that the lightning arrestercomprises a ceramic or other insulating casing i within the upper partof which is housed the conductors 2 which are spaced apart to form aseries of spark gaps 3. The upper part of the lightning arrester isconnected to the line wire or power line by means of the conductor i andis capped by means of the insulating cap The lower part of the arresteris provided with a lower terminal 6 and negative resistance material 7is inte"posed between the lower end of the spark gap structure and thelower terminal 5 in accordance with the disclosure in the patent to I-l.Earle, No. 2,315,320 of March 30, 1943 for AutomaticCircuit-Interrupting Device, owned by the assignee of the presentinvention.

The isolator has the general characteristics of that ol the prior patenthereinabove men tioned, and is composed of an upper terminal indicatedby the reference character 8 and a lower terminal indicated by thereference character 9. The lower terminal is provided with a shell-likeportion In which carries an explosive charge in the form of a cartridgeII. The shell it is spaced from a surrounding lip 92 of the upperterminal and is arranged to be heated when heavy sparking occurs andthereby ignite and cause explosion of the explosive during the flow ofexcessive current from the lightning arrester through the isolator. twoterminals are held in spaced relation by means of a breakable shell 53and. the ground wire i is electrically connected to the lower terminal,such ground wire being grounded as shown in Figure 1.

In order to carry away any accumulated charge, a high value resistor,such as carbon and other compacted materials indicated by the referencecharacter 55, is electrically positioned between. the cartridge and theupper terminal 8. It is held downwardly in firm contact with the upperend of the cartridge H by means of a spring 56 and thus serves as a highresistance connector between the upper terminal 1'3 and the lowertern-anal 9 and thus carries away any accumulated charge prevents theformation of corona or any slight sparking that may cause radiointerference such as hereinabove 1nentioned A simple way of constructingthe upper terminal 8 is to provide a threaded stem ll which screws intothe lower terminal (-3 of the lightning arr-ester, the lower terminal 9being connected to the ground wire Us by means of a screw it, a suitableinsulating shell l9 being provided for this connection.

In the form of invention shown in Figure 3 and 4 the same general ideais employed except in the manner in which the connecting resistor isused. In this form of the invention the upper terminal of the isolatoris indicated by the reference character 29 and the lower terminal by thereference character 2!. The breakable shell or casing of insulatingmaterial is indicated by the reference character 22 and an annularcompacted carbon resistor by the reference character 23. This annular,compacted carbon resistor is a high value resistor and is adapted toconductaway any charge that may accumulate on the upper electrode 2E3.It is electrically connected to the lower electrode because it rests ona flanged portion 24 thereof. It is electrically connected to the upperelectrode 29 by means or a spring spider 25 shown more in detail inFigure 4. This spring spider may have a central aperture 2 see Figure tthrough which the shell 26 of the lower terminal 2! passes, such shellcarrying the cartridge 2'! having, the explosive charge. The springspider has upwardly extending, slightly outwardly sprung spring arms 28which directly engage the conical lower surface of the upper terminal20.

In the form of the invention shown in Figure 5, the upper terminal isindicated by the reference character 29 and the lower terminal by thereference character 36. The insulating shell is shown at 3i as providedwith an internally located, high resistance conducting coating 32 of anysuitable conducting material having the requisite value of resistance.This conducting coating extends from the lower electrode Bil to theupper electrode 29. The cartridge for the explosive charge is indicatedat 33 and is carried in the shell-like portion 34 as hereinabovedescribed.

In the form of the invention shown in Figure 6 the upper electrode isindicated at 35 and the lower electrode at 36. The lower electrode hasthe shell Bl, previously described, which carries the cartridge 38having the explosive charge. The insulating shell or casing is indicatedat 39. The upper and lower electrodes are connected by a high valueresistor d6 whose upper and lower pigtails or terminals 45 and 42 areelectrically connected to the upper and lower electrodes and serve asthe support for the resistor 35.

It will be seen that in each form of the invention the high resistancecarbon or other resistor serves to conduct away any accumulated chargeand to thus prevent the formation of corona or sli ht sparking. However,it does not materially alter the flow of excessive current when suchflow occurs, as in each instance the value of the resistor is very high.Therefore, the explosive charge is exploded in the ordinary way andrupture of the rupturable casing or breakable casing is obtained tothereby electrically separate the lightning arrester from the ground.

Although this invention has been described in considerable detail, it isto be understood that such description is intended as illustrativerather than limiting, as the invention may be variously embodied and isto be interpreted as claimed.

We claim:

1. The combination of a lightning arrester having one end arranged to beconnected to a power line and having a second end, an isolating devicehaving a first terminal connected to the second end of said lightningarrester and having a second terminal connected to the ground, abreakable shell holding said terminals apart, an explosive chargearranged to explode and break said shell on excessive flow of currentthrough said device, and a high value resistor electrically joining saidterminals for normally preventing the formation of a difference ofpotential between said terminals, said lightning arrester including aspark gap electrically interposed between the power line and saidisolating device, whereby neither terminal of said isolating device isconnected to said power line.

2. The combination of a lightning arrester having one end arranged to beconnected to a power line and having a second. end, an isolating devicehaving a first terminal connected to the second end of said lightningarrester and having a second terminal. connected to the ground, abreakable shell holding said terminals apart, an explosive chargearranged to explode and break said shell on excessive flow of currentthrough said device, one of said terminals having a recessed part, aresistor located in said recessed part, and a spring located in saidrecessed part and holding said resistor in electrical connection withthe other of said terminals, said lightning arrester including a sparkgap electrically interposed between the power line and said isolatingdevice, whereby neither terminal of said isolating device is connectedto said power line.

3. The combination of a lightning arrester having one end arranged to beconnected to a power line and having a second end, an isolating devicehaving a first terminal connected to the second end of said lightningarrester and having a second terminal connected to the ground, abreakable shell holding said terminals apart, an explosive chargearranged to explode nd break said shell on excessive flow of currentthrough said device, and a high resistance conducting coating formed onthe inner side of said shell and electrically connecting said terminalsfor normally preventing the formation of a difference of potentialbetween said terminals, said lightning arrester including a spark gapelectrically inter posed between the power line and said isolatingdevice, whereby neither terminal of said isolating device is connectedto said power line.

4. The combination of a lightning arrester having one end arranged to beconnected to a power line and having a second end, an isolating devicehaving a first terminal connected to the second end of said lightningarrester and having a second terminal connected to the ground, abreakable shell holding said terminals apart, an explosive chargearranged to explode and break said shell on excessive flow of currentthrough said device, an annular compacted high value resistor resting onone of said terminals, and a spring bearing on the other terminal andsaid resistor, whereby said resistor electrically joins said terminalsfor normally preventing the formation of a difierence of potentialbetween said terminals, said lightning arrester including a spark gapelectrically interposed between the power line and said isolatingdevice, whereby neither terminal of said isolating device is connectedto said power line.

5. The combination of a lightning arrester having one end arranged to beconnected to a power line and having a second end, an isolating devicehaving a first terminal connected to the second end of said lightningarrester and having a second terminal connected to the ground, abreakable shell holding said terminals apart, an

explosive charge arranged to explode and break REFERENCES CITED saidshell on excessive flow of current through The following references areof record in the said device, and a high value resistor located me ofthis patent; externally of said shell and supported by and electricallyjoining said terminals for normally 5 UNITED STATES PATENTS preventingthe formation of a difference of poten- N b r Na Dat tial between saidterminals, said lightning ar- 1,967,616 I-Iillebrand July 24, 1934rester including a spark gap electrically inter- 2,118,795 Littleton May24, 1938 posed between the power line and said isolating 2,174,477Pittman et al. Sept. 26, 1939 device, whereby neither terminal of saidisolating 10 2,283,685 McCreery et a1 May 19, 1942 device is connectedto said power line. 2,305,436 McMorris Dec. 15, 1942 HERMAN O.STOEL'I'ING. 2,315,320 Earle Mar. 30, 1943 JOSEPH F. KUZELA.

